The community based one tier selection scheme was considered for both breeds as the optimal breeding program for both of the study areas. The community based breeding program is believed to be a more convenient breeding program for such type of production systems which are characterized as low-input system with poorly developed infrastructures (Sölkner et al., 1998; Kahi et al., 2005; Gizaw et al., 2009). The flocks from 30 households with the average of 26 breeding does per household were considered as one breeding unit for Abergelle goat, While the flocks from 60 households with the average of 5 breeding does per household was considered as one breeding unit for Western Lowland goats.
Four selection groups were defined to indicate the selection pathways. A selection group is defined by both, type of parents (one sex) passing genes and type of offspring receiving their genes. The selection groups were Bucks to produce Bucks (B>B), Bucks to produce Does (B>D), Does to produce Bucks (D>B) and Does to produce Does (D>D). Strong selection of male animals was assumed. The assumption was that the genetic gain obtained through selection would be disseminated by the selected bucks. The female animals would be selected only for the replacement. The young bucks at the age of six months would be selected based on their own performance of growth and the information from their dams for others traits. Breeding bucks were assumed to be in use for two time units (two years). Early age of selection (six months weight) was assumed to be more appropriate for the existing production systems of the study areas where negative selection is very common. Farmers tend to sale the fast growing animal at early age to get attractive market price.
The important input parameters of the two breeds for modeling (running ZPLAN) are shown in table 7. The information for the input parameters were derived from the production system, morphological characterization and own flock ranking results of this study and published report of on-farm monitoring studies (Derbie, 2008; Tsegaye, 2009; Derbie and Taye, 2013). The number of proven (candidate) animals in each time unit (year) were projected using the reproductive parameters and survival rate of the breeds. For instance the numbers of proven male animals for Western Lowland goat were calculated as follows: Assuming that sixty participant farmers with the average of 5 breeding does and the total of 300 breeding does in the village selection scheme. Only 85% of them have kidding within one time unit (year), 0.6 year kidding interval, 1.5 liters per kidding, 1.67 kidding per year (time unit), 80% of survival rate and 50 % sex ratio. It gives 255 male selection candidates (300*.85*1.5*1.67*.8*.5=255).
In this study, only the costs of additional activities to the normal management practices were considered as the cost parameters. Those were the cost of performance recording (Enumerator salary, cost of items for animal identification and cost of stationary materials) and cost of drugs.
Those costs were calculated per individual breeding does per year. For instance the costs at Western Lowland goat were estimated as follow:
a) Labor cost for recording: One enumerator for 300 does: Enumerator salary 24.59
€/month=295.08€/year; 295.08€/300 does; 0.98€/doe/year
b) Identification cost: 2 tags/animal/year (a doe and her 2.5 kids/year) 0.2€/tag = 2*3.4*0.2
=1.36 €/does/year
C) Drugs: 0.4 €/animal/year = 3.4 (a doe plus 1.13 kids/year)*0.4 =1.36€/does/year
Table 7. Input parameters for modeling alternative breeding programs
Parameters Abergelle Western Lowland
Population parameters
Population size(Does) 780 300
Number of proven males/years 300 255
Proportion of bucks selected 10% 10 %
Biological parameters
Breeding does in use(year) 5 5
Breeding bucks in use (year) 2 2
Mean age of bucks at birth of first offspring (years) 1.5 1.2
Mean age of does at birth of first offspring (years) 1.3 1.1
Kidding rate .85 .85
Mean time period b/n subsequent kidding (years) 1 .6
Mean number of kids per litter (litter size) 1.13 1.5
Number of kidding/doe/year 1 1.67
Kid survival to six months (%) 80% 80 %
Cost parameters
Animal identification doe/year(€) .86 1.36
drug /doe/year(€) .86 1.36
Enumerator salary(€) .98 .98
Stationary materials for recording(€) .20 .20
Interest rate return (%) 0.05 0.05
Interest rate cost (%) 0.08 0.08
Investment period /year 15 15
3.2.5.2. Alternatives breeding programs
Four different alternatives for each breed were proposed for evaluating optimal breeding program (Table 8). The alternatives were based on the variation of the number of the traits in the selection index (recording) while keeping all traits in aggregate breeding goal. The important considerations of the alternatives were to see the effect of the variation of the number of traits in the recording scheme (selection criteria) on the genetic gains of the individual traits as well as the aggregate response. Since the selection program will operate at village level, inclusion of all traits in recording scheme might not be feasible in technical and economical terms.
Table 8. Alternative breeding schemes for Abergelle and Western Lowland goats
Alternatives Breed
Abergelle Western Lowland
1 All traits in the selection
index(SMW+DMY+PKW)
All traits in the selection index(SMW+NKB+PKW)
2 SMW+DMY in the selection
index
SMW+NKB in the selection index 3 SMW+PKW in the selection index SMW+PKW in the selection index 4 Only SMW in the selection index Only SMW in the selection index Note: SMW=Six months weight, DMY=Daily milk yield, PKW=Proportion of Kid weaned, NKB=Number of kids born
3.2.5.3. Genetic and phenotypic parameters
The genetic and phenotypic parameters are presented in Table 9. Due to the population parameters of the study breeds lacking, the weighted heritability estimates of the traits from published reports of other local and exotic goats were used (Odubate et al., 1996; Bosso et al., 2007; Valencia et al., 2007; Rashidi et al., 2008; Chun-yan Zhang et al., 2009; Alade et al., 2010; Faruque et al., 2010; Mantaldo et al., 2010; Kebede et al., 2012a). The genetic and phenotypic correlations of the traits were obtained from published reports on sheep (Abegaz, 2002; Matika et al., 2003; Gizaw et al., 2007; Afolayan et al., 2009).
Table 9. Phenotypic correlation (above the diagonal), genotypic correlation (below the diagonal) and heritability of the traits (along diagonal)
Traits Abergelle Western Lowland
SMW DMY PKW SMW NKB PKW
SMW 0.28 0.1 0.1 0.28 0 0.1
DMY/NKB 0.2 0.32 0.14 0 0.10 0.15
PKW 0.3 0.53 .05 0.3 -0.20 0.05
Note: SMW=Six months weight, DMY=Daily milk yield, PKW=Proportion of Kids weaned, NKB=Number of kids born